1. Field of the Invention
The present invention relates to the method and device used for eliminating the image overlap blurring phenomenon between frames in the process of simulating CRT impulse type image display, and more particularly, to the method and device used for eliminating the after image overlap blurring phenomenon between frames in the process of simulating CRT impulse type image display with liquid crystal display (LCD).
2. The Prior Arts
In recent years, liquid crystal display (LCD) device have been very popular and widely used, and the varieties of its products are enormous, from the consumer electronic products to computers and the mobile phone wireless communication applications, such that the technology progress and development of the LCD device is rapidly advancing, and its trend is in agreement with the future trend of the development of the electronic products toward the features of light weight, thin thickness, short length, small size, low power consumption, and low heat dissipation, etc. And especially the development and progress of the technology of the Liquid Crystal Display is sufficiently advanced to overcome the restrictions and shortcomings of the traditional and the present displaying technologies such as Cathode Ray Tube (CRT) or Light Emitting Diode (LED), and it plays an important role in the development and application of computer, communication equipment and other consumer electronic products, and thus the LCD technology does indeed have great future and potential in this field.
The flat display effect of LCD is apparently superior to the image display effect of CRT, and in addition, its power consumption and its heat dissipation are much lower than those of the similar size CRT display. Therefore, this type of display is usually considered as suitable to use in the following applications: portable (mobile) phone display unit, TV receiver, display, and panel in exhibition center or advertisement applications.
In addition, for the LED utilized widely at present, which is subject to the limitations in various practical applications due to its inherent characteristics, such as, the LED is preferably used in the static display for numbers, characters, or images, and is not comparable to and can not match the LCD technology which is capable of dynamic image display and be able to achieve the effect of liveliness and vividness.
Presently, the televisions and display devices made with the technology of liquid crystal display have been produced in large quantities, to replace the televisions and display devices made with the conventional CRT. However, in the liquid crystal display technology of the present days there still exist drawbacks and limitations that must be overcome and improved.
With regard to the image display of CRT, it utilizes the “impulse type “image display. It produces light emissions by means of irradiating a single electron beam on the pixels coated with fluorescence materials. However, the pixel only produces the emission of light in an instant of a minute portion of time in each frame period. Therefore, it seems that almost no visional overlapping phenomenon will be noticed for the images displayed between the frames.
However, for the LCD image display, it utilizes the “hold type” image display due to the intrinsic property of the LCD material. It produces the image display through the optical response (namely, the gray level response) by means of applying driving voltages on the LCD material. Nevertheless, due to the limitation of the intrinsic property of the liquid crystal material, the image it displays occupies the predominant portion of time of that frame. And for each time its image changes, its luminance (or brightness) also changes step-wise sequentially. Therefore, from the viewpoint of the spectators, he may feel the overlapping of the image of the new frame on that of the old frame, thus creating the blurring of the image outlines and producing the phenomenon of the so-called “after-image”.
In order to eliminate the above-mentioned after image produced by the LCD display device slow optical response, and the resulting image outline blurring phenomenon, currently most LCD television manufacturers try to convert the “hold type” image display of the LCD displaying device into the simulated (or pseudo) impulse type LCD displaying device similar to that of the CRT displaying device, by means of a kind of the so-called “over drive” technology, with its image only occupies a portion of the frame period, namely, the image is not displayed during a portion of each frame period.
The method utilized in this technology is a kind of so-called “over drive” method. It applies to the liquid crystal material the voltage (for example code 200) which is much higher than the originally set target voltage for example code 120), thus expediting and accelerating the optical response speed of the liquid crystal molecules, and accelerating them to reach the predetermined optical response value, and as such shortening the liquid crystal gray level response time to less than one frame period.
However, even the LCD display device made with this kind of over drive technology is able to shorten its gray level response time to less than and within one frame period, yet due to the intrinsic property of the liquid crystal, the generation of its optical response is slow so is its decline. Therefore, the image overlapping and the image outlines blurring phenomenon of the “after image” for the images displayed still can not be eliminated completely.
In order to completely eliminate the “after image”, presently there are three methods adopted by the prior art, which are listed as follows:
(1) writing black data or black images into the frame in the remaining portion of that frame period after the original formal image is displayed;
(2) shutting off the backlight, for example, the blink light method as announced by Hitachi;
(3) the combination of the above methods (1) and (2), namely, both writing in black image and shutting off the backlight.
And in the following we will explain in detail their respective drawbacks and limitations.
However, the three above-mentioned methods have the following drawbacks and limitations, therefore their effects are not ideal, so that the “after image” overlap blurring phenomenon between frames still exists on the LCD screen: (1) necessitating the extra cost and expense of the additional equipment of frequency doubling device or backlight blinking equipment; (2) the electric magnetic interference incurred by the addition of such equipments; (3) for certain liquid crystal materials, their optical responses are fast from brightness to dark, and are slow from dark to brightness; but for other liquid crystal materials their optical responses are slow from brightness to dark, and are fast from dark to brightness.
In order to achieve for certain the effect of eliminating the phenomenon of “after image” overlap blurring displayed on the LCD display screen, the inventor of the present invention proposed a “Method And Device Used For Simulating CRT Impulse Type Image Display” in pending Taiwan Patent Application No. 98103825 to overcome the shortcomings and limitations of the prior art. In that pending paten application, the proposed method and device are mainly characterized in scanning the black lines, which is different from the prior art. By utilizing that proposed method and device, the period of the control voltage pulse used for the image display can be shortened to less than 8.3 ms (which corresponds to 120 Hz), and for which this period is adjustable, and the intervals of the scanning black lines applied during this period is also adjustable. As such, it can be applied to the various optical responses of various different liquid crystal materials, so as to achieve for certain the purpose of simulating CRT impulse type image display. Besides, it can avoid the extra cost and expense of the additional frequency-doubling device of the prior art and the resulting electric magnetic interference. In addition, the inventor of that patent application provides six Embodiments to attain similar but better effects, and thus achieving the important advance and breakthrough of the similar technology in this field.
However, for certain liquid crystal material its optical response is slower from brightness to dark, and during the black line scanning interval its optical response has not yet reached the sufficiently low value. As such, some of them still result in the phenomenon of certain “after image” overlap blurring. In order to thoroughly eliminate this phenomenon, and effectively achieve the ideal effect of simulating CRT image display with LCD display, the present inventor has dedicated his expertise, experience and ingenuity to the research and development of this subject, so as to bring about the realization of the present invention, and which will be discussed in detail as follows.
As such, the present application is the continuation or extension invention of the inventor's another pending Taiwan Patent Application No. 98103825, with its purpose as solving and improving the problem of image overlap blurring between frames in the process of “simulating CRT impulse type image display”. However, as to how to scan the black lines to achieve “simulating CRT impulse type image display with LCD display”, please refer to the prior patent applications of the present inventor, which will not be repeated here for brevity's sake.